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Re: Tek 465 no display
On Thu, 28 Jun 2018 19:57:26 -0700, you wrote:
I'm so sorry that I havent kept up with all of the help here, Albert. I wasn't expecting such a willingly helpful group when i joined the group. This has been an exceptionally busy June for me. I'm recovering from recent heart surgery and seem to be falling behind on my lab repair work among other things. But i did get a bit of time [about 30 min] to follow up on some of the suggestions here. The access board layout diagram is pretty hard to read and not all that much is labeled on the actual board so it is going slower for someone used to point to point and turret board electronics. I have almost zip experience with transistors or pcb layout. But I'm determined to get this figured out.You might, for the sake of general learning, get some breadboard kits, general purpose transistors, and start breadboarding some transistor amplifiers and switches. It would give you a feel for the parts. For PCB layout, consider that you are doing the same as wiring a breadboard (the type with millions of holes). The rules, though, is that the traces cannot cross each other on the same side (otherwise they're the same trace). They must go from layer to layer through a plated through hole called a via. On dual layer boards, you have simply a top and bottom, and the vias go all the way through. On 4 layer boards, there's a top, bottom, and two inner layers. Frequently, some of the layers are reserved for power and ground. So PC boards are not all that bad. You might want to look at linear supplies and how they work. The principles between a linear regulator for tubes and transistors are identical, but the different parts will give you different voltages on the transistors (vs the tubes). Depletion mode N channel FETS are most like tubes, once you get to that point. (triodes, thank you). As in any such project, suspect the power first, then look at functional blocks. I've had 468's with high voltage resistor network problems, which will throw off the high voltage. There's a high voltage divider network that's part of the feedback from the high voltage output back to the regulator. Harvey
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Re: TDS 380 won't trigger
On Fri, 29 Jun 2018 at 00:19 Gary Appel <garyappel@...> wrote:
It's alive!Excellent - congrats on the fix. |
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Re: Dead 7603
On 06/28/2018 09:07 PM, garp66 wrote:
hi all,Which "above written description" are you talking about?? Unless you quote from the email you are replying to, we have no idea what you are talking about.? Notice how I quoted your email reply?? Now folks know who and what I'm replying to, and have the context of the conversation. Top or bottom replying is a religious discussion for another day. Mark |
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Re: Kludging together a TDR or similar?
I really like 1502 (not a, b, 1503 etc), and have some I ought to sell.
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There are two principal weaknesses other than the usual PSU caps: * the tunnel diode is relatively fragile, and can be destroyed by a DC voltage on the cable or even a static charge in the cable - hence the special shorting BNC connector. Having aid that, all 5 that I have seen are intact * the battery pack must be present before it will switch on: the PSU detects missing and uncharged batteries. All 5 that I have seen have had faulty batteries. There are ways of faking a battery, or they can be replaced by new sub-C NiCds or NiMH. With NiMH be very careful with "Chinese capacity specifications" and the trickle charging current. On 29/06/18 04:09, Pete Lancashire wrote:
Yeah if you need the short distance performance the 1502 is the only way to |
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Re: Tek 465 no display
Sorry to hear about your health problems Russ. First things first of course.
There you got me! I remember I was typing with the laptop on my knees. I had to look skew at the manual and though I even checked twice I made this mistake. Success, Albert |
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Re: Tek 422 ac/dc power supply issues
just checked to see that pictures aligned with the text...NOT!? it is a mess, not sure how to fix that, nor am I sure how/what happened. ended up with some of my pwr sply too! hmmmm all out of order.
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I will deal with it later. sorry for the mess ¸é±ð²Ô¨¦±ð On 2018-06-28 03:28 PM, ¸é±ð²Ô¨¦±ð wrote:
Hi Jeff- |
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Re: Kludging together a TDR or similar?
If lightning hit that drop, there is likely more than one damaged area, or even long stretches of the shield is gone. I worked in CATV repairing the electronics and I have seen damaged coax where the entire outer conductor had vaporized. The worst damage is usually at sharp turns, like the corner of a building. We often had to run temporary drops to replace buried lines, until or Ditchwitch was available to bury it. This was in the Cincinnati area, so lightning was a big problem. It wiped out thousands of power transformers in the set top boxes, as well.
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There should be a tap to reduce the signal level to the modem which may also be damaged. It is usually at the house end of the drop, and it is easily damaged by lightning. Mine is 17dB. Michael A. Terrell -- -----Original Message-----
From: Kevin Oconnor <kjo@...> |
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Re: TDS 380 won't trigger
It's alive!
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The parts arrived today. I replaced the acquisition RAM with a MB8464 - not the original part, but it appears that the original part was unobtainium. The 'scope now displays traces correctly at all sweep rates, and the offset and calibration are again correct. Thanks again for pointing me to the information on EEblog, and the technical manual. Gary Appel -----Original Message-----
From: Siggi Sent: Sunday, June 24, 2018 6:32 AM To: [email protected] Subject: Re: [TekScopes] TDS 380 won't trigger On Sat, 23 Jun 2018 at 20:45 Gary Appel <garyappel@...> wrote: Thank you Siggi. At low sweep speed, where the trace rolls across the screen, the 'scope isIf you've tried to run signal path compensation after the acquisition system wonked out, this could be working as intended. The acquisition system will have been used to measure the DC offset to compensate, and it could have measured a large "ghost" offset. Most of the IC's have a '95 date code. The Dallas chip has a '96 date code. It is certainly on borrowed time. I have seen a number of references toI'm not sure it's worth the effort to preserve the memory contents of the NVRAM, as the calibration procedure for this scope looks like a piece of cake. All you need is some DC and a "fast rise" (<10ns) pulse generator. This is pretty typical for the CCD-based scopes, it was easy as pie to calibrate my 2430 using what I already had around the lab, plus some spit and bubblegum. I do have an analog 'scope as well - a 2465A, that is also likely onPiffle - my 2467 has a keeper with an '85 date code in it, and it's still going strong :). Of course I'm set to calibrate it, should the keeper give up the ghost, so I'm not too bothered - I'm quite curious to see how long the battery will last. It sounds like my first task should be to replace that acquisition memory.Yups, sounds like. Meanwhile, in my impatience, I just ordered a replacement 'scope. It'sGood luck! |
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Re: Kludging together a TDR or similar?
Yeah if you need the short distance performance the 1502 is the only way to
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go. The newer models which have LCD redoubt if the LCD has not gone bad now it will. And the unfortunate part is the LCD was custom. keep your eyes open a lot of sellers don't know what they have but like another member said make sure the tunnel diode is good. A few people have looked at the ex Soviet tunnel diodes but as far as I know no one has found a substitute. To me sounds like a perfect project to use a modern pulsar there are an awful lot of 1502s out there. On Thu, Jun 28, 2018, 1:00 PM Harvey White <madyn@...> wrote:
On Thu, 28 Jun 2018 11:02:57 -0700, you wrote:As Stefan said, how fast a step pulse you need and how much scopebandwidth you need both depend on how much resolution you need. Do you |
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Re: Kludging together a TDR or similar?
TV coax problem....
As noted, u don¡¯t indicate the run length u have. If it goes from ur house terminal to the typical green post in the yard and it is 100ft or less, it would be more efficient to just run a new coax over the ground to verify operation. If you have buried coax with a fault, I wouldn¡¯t trust any of it. Kjo Sent from kjo iPhone |
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Re: Tek 465 no display
I'm so sorry that I havent kept up with all of the help here, Albert. I wasn't expecting such a willingly helpful group when i joined the group. This has been an exceptionally busy June for me. I'm recovering from recent heart surgery and seem to be falling behind on my lab repair work among other things. But i did get a bit of time [about 30 min] to follow up on some of the suggestions here. The access board layout diagram is pretty hard to read and not all that much is labeled on the actual board so it is going slower for someone used to point to point and turret board electronics. I have almost zip experience with transistors or pcb layout. But I'm determined to get this figured out.
One question: did you mean c1549 and cr1549? You were mentioning the 15v rail and c1559 and cr 1559 are on the 5v rail. Re the video, it was the model and post sn 250000 that caught my eye an invoked my comment. Misery likes company and to see someome trying to fix a no screen problem gave me a bit of hope. There is not much other video tutorial that I could find, good or bad, re what i have a problem with. I am completely self taught in electronics and despite recognizing the less than stellar technique, I actually learned a little about layout even if nothing else was up to par judging from the comments. I knew almost nothing about this 465 before I started this thread and I'm gaining ground. Poco a poco andamos lejos. Thanks again to all for the patience and wealth of info. I have a birthday on Saturday. Maybe i will have time to spend a few more hours figuring this out. Seeing a trace on the screen would be way better than candles. ? |
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Re: Dead 7603
hi all,
The above written description is quite good, and clear. Due to diversity in human nature, sometimes a picture or video supplementing information for a procedure can be helpful to some, including the uninitiated. I wonder if some Tektronix YouTube 'expert' videos might be linked to some discussions ? We all gain with additional clarity, helps prevent accidents, and it seems that added image/video teaching tools have proved themselves over text-only technology. Tekscopes List evolution ? |
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Re: Kludging together a TDR or similar?
You might want to try doing a web search on terms like those below to find some other ideas too.
A TDR is not the only way to find a cable break. You can find where a signal fed into a cable is attenuated or where it is stronger. use oscilloscope find cable break find burried cable break Some suggestions: Regards, Brian. |
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Re: Tek 422 ac/dc power supply issues
Hi Jeff-
I have the little bugger up and running using 2n5881 xstrs, runs 2.5A draw at 11.5V and ~900ma at 26V scope runs all the way down to 10.5V!!!! all of this is little at a time when I have 10-15 min to look into things. So.....without the feedback and -12v it will do exactly as it has been doing : 140us square wave (actually 280us) on time driving the finals, no 15us pulse modulation on and 115us off for each xstr. (aprox us numbers), making lots of heat! Still too much current as turn on time just too long. I decided that it was time to pull Q1174/84 and make test mode look at the base drive while running just the pwr sply no load. Test mode-? ( as expected circuit draws very little current and runs very cool in this mode described below.) I? tied? D1232/3 junction to D1242/3 then to +12.5V and D1244/5 to -12.5V, Gnd is Batt Neg = connection/common, 0V. Tying the 12v feedback and the generated 12v together allows the -12V (error Amp section) to function yielding proper V on both sides of R1162 (tunnel diode and B of Q1164). Q1174 and Q1184 are pulled, picture is on the base of each from T1171 (secondary). waveforms appear to be close to what are in schematic. the -12V adj does make some minor change in the form of stability and noted the Voltage change monitoring Base of Q1164, osc freq is near minimum adj point. The 12V start regulator is working. (Q1193/4) previously tested. No pulse modulation from pulse amp section all else is working.......Q1163 had been replaced by previous person- un-marked part, should be 151-0087-00 = 2n1131 per the manual, 2n2905 should be fine per another book. Voila pulse modulated base signal. nice and cool with pretty waveforms to drive the base of Q1174/84 /g/TekScopes/photo/44362/8?p=Name,,,20,1,0,0 plugged in the Q1174/84 and the scope. nope not working yet! which brings me to the issue of why it is not generating its own +/-12V to cause the rest of the circuit to begin? functioning. hmmm....all that is left is T1201 since all components are good...even with subs for the final amps. I am thinking a diode needs to be added to get the feedback to begin..but should not need to kick start that way. I am missing something. guess I need to look at output side of T1201 again. I think this thing should run without a load! so I disconnected the load (scope...I know bad for soaring voltages) and again Voila working voltages...yes way high like really high 16V on the 12V line etc... but working with very low current draw....even with a very low 10V input. So time to go find faults in the scope itself......found other faults caused by someone not putting connections back on correct pins in the scope! once I solved that issue, replaced one cap that was leaky acting more as a resistor most likely due to reversed V from above pins reversed. Power it again and pop...the 110V doubler diodes and C1224 went bad ( now a 10uf 200V 105C cap from the used bin). i had shoved in 1n4004 ( what I had on hand), high voltages suffered ( i did not think they were fast enough, and they were not)...but it was working!!!! I had to wait three weeks until my path allowed me to stop and obtain some 1n4936 ( seems more than adequate) and other misc parts- heat sinks...so as to mount xstrs correctly on the side I do want to match the 2N5881's better ( i have a bag of them along with 2n3055's and 2n5882's I obtained from a swap a month back). The heat sinks mounted on the side will allow me easily as time permits to play with other xstrs, and I did not want to split the supply apart to drill and mount on the original area. I may find another 1899? (most likely not) /g/TekScopes/photo/44362/7?p=Name,,,20,1,0,0 ?weeks later--test continuation after heat sink install....I did try a pair of 2n3055 ,sort of worked but heated way too much...must be the capacitance, so pulled them and went back to a different matched pair of 5881's. I did notice a little anomaly/ spike on one side and a bit more ring at 11.5V something to think about later. /g/TekScopes/photo/44362/16?p=Name,,,20,1,0,0 /g/TekScopes/photo/44362/18?p=Name,,,20,1,0,0 Well it works great all the voltages came into spec, Hooray! so I figure time to stop install another thermal sensor on the new kluge heat sink and finish this so I can use it! /g/TekScopes/photo/44362/8?p=Name,,,20,1,0,0 besides it is now my busy season repairing woodwinds and music performances . i posted pictures- hope the titles say enough most are 50 or 20us on Collector side, 20V/div, for the base 1V/div, oh 11V on picts means 11.5VDC input and 26V means 26.5VDC 11.5V stuff: /g/TekScopes/photo/44362/17?p=Name,,,20,1,0,0 /g/TekScopes/photo/44362/10?p=Name,,,20,1,0,0 /g/TekScopes/photo/44362/9?p=Name,,,20,1,0,0 26.5V stuff: /g/TekScopes/photo/44362/2?p=Name,,,20,1,0,0 collectors /g/TekScopes/photo/44362/20?p=Name,,,20,1,20,0 /g/TekScopes/photo/44362/11?p=Name,,,20,1,0,0 /g/TekScopes/photo/44362/12?p=Name,,,20,1,0,0 bases /g/TekScopes/photo/44362/9?p=Name,,,20,1,0,0 hope this helps someone else in the future....especially replacing 2n1899 unobtanium xstrs...I saved both the good one and the bad one. just better to do both! ¸é±ð²Ô¨¦±ð |
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Re: 2215 dim crt poor focus.
Hard to tell by that waveform. To get it as pictured you need to set everything just like they did when they drew it, or theoretically set it. With that auto intensity control you should be able to make the amplitude levels they call for, The timing and setting of the sweep will affect the times, which is less important. However none of that should affect the focus.
Since there are really no CRT testers that work right on scope tubes, the most effective check is to boost the filament voltage. You could maybe take a 9 volt battery and use some wires with good insulation, put a 1N4007 in series and get about 8.5 volts to it. If it improves, then you know. At that point, well I seem to find ways, add a loop through the core of the HV transformer, one time it was DC and I modified that instead. Sometimes I just do it as a test, but that can be a PITA. On many you have to get into the HV cage and disconnect a wire, hope whatever you use holds up to the voltage, and don't really know exactly how much boost you get out of each added winding. So the battery trick is better in some cases, just insulate it, put it on wood or something that has NOT been soaking in anything since 1953 (old Redd Foxx party album joke), put the scope on isolation and don't ground it to anything, use the internal calibrator or whatever to get a waveform. That should be safe enough. When you get to modifying then you can see the results, and use a battery powered meter to measure the filament voltage. No matter what, for beam current/emission that is probably the best most practical test we have. i think other failure modes are extremely rare, when was the last time you saw a scope CRT with a short, or gassy, or an open element ? Not recently I would bet. |
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Re: Kludging together a TDR or similar?
Alan Wolke did a video on TDR using a scrap box ~1ns pulser: <
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>. For ~$2 and a few minutes soldering, you might be able to get useful results :). On Thu, 28 Jun 2018 at 13:29 cheater cheater <cheater00@...> wrote:
Hi everyone, |
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Re: Kludging together a TDR or similar?
Yes. The velocity of propagation depends on the dielectric constant of the center insulation and my memory says the impedance of the cable. There are extensive charts of cable and air line coax that give the velocity of propagation. Typically, it is about 75% of the speed of light in a vacuum. Some TDRs have built in calibration for common cable types.
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I used TDRs quite a bit in the past mostly for matching lengths of video cables. They can be very useful instruments. The TDR can also measure the velocity of propagation if the distance to a discontinuity is known. From that one can derive all sorts of other information about a cable including its impedance. On 6/28/2018 11:04 AM, cheater cheater wrote:
Thanks. Does the propagation time depend on the coax type? --
Richard Knoppow dickburk@... WB6KBL |
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Re: Kludging together a TDR or similar?
You should perhaps more specifically define "broken" in the context of the discussion.
As I said earlier, measuring the C on an open cable is way easier than TDR. I have all sorts of stuff for TDR (7S12 and such), but If I were to do fault-finding searches in my house cable plant, I'd start with simple continuity measurements, then capacitance. It's a PITA to set up for TDR, and interpret the results - especially for a novice. You'd have to find the proper cable velocity factor and impedance, match the impedances, and do a bunch of figuring out and interpeting* what's going on. With a C-method, you just need simple quantity measurements and simple calculation of the measured C divided by the C per foot to estimate the distance from the test end to the break. Here's an example site with some info - one of many easily found: I'm guessing that the purpose is to estimate the location - like in a wall or such, to assess the grief associated with repair. Or, to figure out who will pay for the repair - the cable company or you. Generally, the cable company owns and maintains the outside plant, up to where the service enters your house. So, all you need to worry about is from that point inward. If you can confirm that your cable is intact from there to the modem, you're all set. The point of demarcation should be the safety ground connector, where the company's cable enters, and your cable leaves. There will be a fairly heavy ground lead attached, that then runs to a convenient earth ground like a metal water pipe or ground rod. If the cable goes from there directly to the modem, it's just a simple continuity test. If there is indeed an open, then the C test can help see how far it is from either end. If the cable is part of a distribution system in the house (your inside plant), then there may be all sorts of splices, power splitters, possibly amplifiers, and other cable boxes and TVs, etc, that will interfere with simple tests and TDR* too, so you have to know what's in there and where everything is physically. If you already have it isolated to a single run of cable, and just need an answer, then keep it simple. If you don't have it isolated in this way, then unknown devices or connections may confuse the issue regardless of methods. If, on the other hand, you want to learn about TDR, then this is a good place to do it, so carry on. *Notes from above - imagine launching a TDR pulse into any port of a black-box house cable plant loaded with all kinds of devices, with all kinds of cable interconnect lengths, and what comes back. Virtually none of typical devices are broad-band matched, so there likely would be a very interesting, but useless picture. You'd still have to have more info about what's in there, and isolate it to a single run for best results. A frequency domain approach would be a better alternative for at least proofing the whole plant, as-is, RF-wise. For example, put a VHF test signal in at the head, and look for it coming out at reasonably proper levels at each port. One last note - I would advise against anyone arbitrarily hooking up a TDR system to any cable plant, whether it's for cable or satellite service, without first being absolutely sure that no DC power is present, or can inadvertently be applied. DC is often used on the cables for powering and signalling remote and in-line devices, so could damage the TDR equipment - an expensive lesson indeed. Ed |
Michael A. Terrell
Jeff Urban
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